Spark plug



Feb. 16, 1937. L BROKAW 2,070,708

SPARK PLUG Filed May 4, 1936 INVENTOR J. Bro/(aw Patented Feb. 16, 1937.

UNITED STATES PATENT OFFICE 2 Claims.

The invention aims to provide a new and improved engine spark plug having a normally closed but readily opened passage so located and of such size that the spark jumping across the spark gap may be readily viewed when the engine is cranked slowly by hand, such inspection being performed while the engine is cold and will not fire when slowly cranked.

A further object is to provide an improved construction which enables testing of the plugs of an engine while the latter is running, in much the same manner as when testing an engine equipped with pet-cocks, that is, by opening the passages of the plugs to determine whether flame leaves such passages at regular intervals.

A still further aim is to provide an improved renewable valve means for normally closing the plug passage.

Yet another object is to provide a construction in which any carbon which may accumulate in the plug passage, may be readily removed by means of an ordinary wire nail or the like.

A still further object is to provide an exceptionally simple and inexpensive construction, yet one which will be efficient and durable.

With the foregoing in view, the invention resides in the novel subject matter hereinafter described and claimed, the description being accomplished by reference to the accompanying drawing.

Fig. l is a vertical sectional view partly in elevation showing the improved plug, the inspection and testing passage being open, the view being taken substantially on line I-I of Fig. 2.

Fig. 2 is an upper end view.

Fig. 3 is a perspective view of a portion of the insulator illustrating the manner in which it is grooved in forming the passage.

Fig. 4 is a lower end view.

Fig. 5 is a sectional view with the valve means removed illustrating the manner in which flame escapes through the passage when the plug is properly firing the cylinder charge.

Fig. 6 is a perspective view of the renewable seat ring of the valve means.

The plug body I is of conventional one-piece form, the lower end of said body being provided with the usual screw threads 8 and electrode 9. The upper end of the body 'I is provided with an 50 upstanding externally threaded neck I0 which snugly surrounds the usual porcelain insulator I I, which insulator carries the usual central electrode I2, spaced from the electrode 9 to form the spark gap H3. The upper end of the body is pro- 55 vided with a fiat face I4 around the neck I0, and

one peripheral groove IS in its enlargement I1, 10

and with another downwardly flared groove I8 in its downwardly tapered portion I9, the grooves I6 and I8 being in alinement with each other and in communication. The interior of the body I is formed in the present showing with one 15 groove opposed to the upper end of the groove I8 and communicating therewith, said groove 20 extending from the lower end of the groove I6 into the space between the lower end of the body I and the lower end of the insulator II. The upper end of the passage I5 is formed by an 20 opening 2| which is preferably upwardly flared to some extent as shown, the lower end of this opening being in communication with the groove I6.

Due to the straight downwardly flared form of the passage I5, and to its location and size, the spark gap of the plug is visible through said passage when the latter is open. Thus, by having someone slowly crank the motor with the ignition switch closed, another person may look through the passages I5 of the various plugs to visually inspect the spark, and the downwardly flared form of said pass-age also renders a large portion of the combustion chamber visible. When the engine is to be tested while running, the passages I5 of the plugs may be readily opened and it may be seen at a glance whether flame is being blown from said passages at regular intervals.

Novel valve -means is provided for normally closing the upper end of the passage I5 and for opening said passage whenever desired. A valve ring 22, preferably of right angular cross section, is threaded upon the neck I0 and is provided with a peripheral notch 23 which I prefer to make of greater size than the opening 2I so that the notch and opening need not be accurately alined when it is desired to open the passage l5. A renewable metal seat ring 24 is interposed between the valve ring 22 and the flat face I4 of the plug body I, a said seat ring being provided with a transverse split 25 of a width substantially equal to the width of the notch 23. The ends of said ring 24 are bent upwardly to provide lugs 26 which lie against opposite sides of said notch to so inte r- 55 look the seat ring 24 with the valve ring 22, as to insure unitary rotation thereof. Normally a portion of the seat ring 24 spaced from its notch 25, extends over the opening 2| and tightly closes the latter, but the ring 22 may be readily turned with a wrench or pair of pliers to bring the notches of the two rings 22 and 24 into registration with said opening, for either visually inspecting the spark while slowly cranking the cold motor, or for testing the firing of the engine while operating.

It will be seen from the foregoing that novel and advantageous provision has been made for carrying out the objects of the invention. While the details disclosed are preferred, minor variations may be made within the scope of the invention as claimed.

Due to the fact that very little of the passage I5 is formed through metal, little carbon will accumulate in said passage, and what small amount does accumulate may be readily cleaned out by forcing a wire nail or the like downwardly through said passage.

Shouldthe seat ring 24 become so scored, worn or pitted as to require replacing with a new ring, this may be readily accomplished by unthreading the valve ring 22 from the neck I 0.

I claim:

1. An engine spark plug comprising a metal body having an electrode at its lower end, a central electrode-carrying insulator secured in said body, said body and insulator being jointly formed with a straight inclined downwardly flared passage which opens through the upper end of said body and through the lower end of said insulator, said passage consisting primarily of one groove in the periphery of the insulator and a registering groove in the inner side of the body, the remainder of said passage being formed by a short opening extending from the insulator groove to the upper end of the body, said pass-age being so located and of such size that the spark gap of the plug and the spark may be viewed therethrough when the cold engine is cranked slowly by hand, and means for closing said passage until the spark is to be visually inspected or the plug is to be tested with the motor running.

2. In an engine spark plug having a body, a central insulator secured in and projecting above said body, an externally threaded neck projecting upwardly from said body around said insulator, a flat upper surface on the body around said neck, and a passage which opens through said flat upper surface; a valve ring threaded upon said neck and having a peripheral notch to register with said passage when said valve ring is turned, and a fiat transversely split seat ring interposed between said valve ring and said fiat face of the body, the gap between the ends of said seat ring being in registration with said notch, said ends of said seat ring being bent upwardly and providing lugs which lie against opposite sides of said notch to interlock said seat ring and said valve ring for unitary rotation.

JAMES ISAAC BROKAW. 

